fix(kvm): close browser websocket immediately on AMT disconnect

[nmgaston]

NOTE: Use with sample-web-ui PR: device-management-toolkit/sample-web-ui#3159

Problem

When an AMT device disconnects (e.g. the device is powered off or the network drops), the KVM/SOL/IDER session would appear frozen in the browser UI. The browser websocket was only closed after ListenToBrowser unblocked from its ReadMessage call, which could take up to 30 seconds (the inactivity timeout) or indefinitely if the browser wasn't sending data.

Fix

In ListenToDevice, the deferred cleanup now immediately sends a websocket CloseMessage to the browser and closes the connection before cancelling the context. This means the browser receives the close frame as soon as the AMT device side drops, allowing the UI to update without waiting for ListenToBrowser to unblock.

Changes

• internal/usecase/devices/interceptor.go — updated the ListenToDevice defer to send websocket.CloseMessage and call Close() on the browser connection before cancel()
• internal/usecase/devices/interceptor_private_test.go — added TestListenToDeviceClosesWebSocketOnAMTDisconnect to verify WriteMessage(CloseMessage) and Close() are called on the browser websocket when the AMT side disconnects

[Copilot]

Pull request overview

This PR improves KVM/SOL/IDER session teardown behavior by proactively closing the browser WebSocket as soon as the AMT/device side disconnects, preventing the UI from appearing “frozen” while ListenToBrowser remains blocked.

Changes:

• Updated ListenToDevice cleanup to send a WebSocket close frame to the browser and close the connection immediately on exit.
• Added a private unit test to verify CloseMessage + Close() are invoked when the AMT side drops.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
internal/usecase/devices/interceptor.go	Sends CloseMessage + closes browser WebSocket in ListenToDevice defer; minor comment tweak near length casting.
internal/usecase/devices/interceptor_private_test.go	Adds a spy-based unit test asserting the browser WebSocket is closed when AMT disconnects.

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[graikhel-intel]

@nmgaston thanks for doing this! Madhavi and I were able to test this today and it’s looking good.

One minor improvement could be around logging. It might help to add a message like: KVM websocket session for <UUID> was closed by AMT.

This would make it easier to debug customer issues where it’s unclear whether the user/browser closed the KVM session or if AMT closed the connection

[RosieAMT]

🎉 This PR is included in version 1.22.2 🎉

The release is available on:

• GitHub release
• v1.22.2

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